## Probabilities

A probability [that an event occurs] is a number between 0 and 1.

### Logical Or

If the probability for an event occuring is given and the probability for another event (disjunct from the first) occuring is given, then the probability p of *either (or both)* occuring is:

### Logical And

If the probability for an event occuring is given and the probability for another event (disjunct from the first) occuring is given, then the probability p of *both* occuring is:

If the probability of an event is known, and this event can only happen after some other event with probability happened, then the probability p of the event 1 happening is:

(this is a special case for independent events)